Under the hood: What’s new in Exchange Server 2019

I had a conversation with a peer about a year and a half ago. We were discussing whether or not Exchange Server 2016 was the end of the road for Microsoft as far as on-premises mail solutions go. The peer that I was discussing it with believed at the time that there might not be another version of Exchange ever released. I thought there might be one more version before Exchange moves entirely to the cloud.

Exchange Server lives on for at least one more iteration with Exchange Server 2019.

Along with the newest version of Exchange Server, comes several new features, services, and technologies. However, Exchange Server 2019 also ushers in the retirement of some features and services as well. In this article, we’ll talk a bit about what new features and technologies Exchange 2019 brings to the table. We’ll break things down into several sections, including security, performance, and end-user experience. We’ll also talk a bit about what features have been removed from Exchange 2019, as well as what features are being de-emphasized.

So, what’s new with Exchange Server 2019 for organizations transitioning from Exchange 2016?


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If you are currently running Exchange Server 2016, the most visible change from a security perspective is the fact that Exchange Server 2019 supports Windows Server Core. Support for server core means a more secure deployment since there is less attack surface and fewer moving parts to deal with.

In addition to the improved security footing that installing on server core brings, Exchange Server 2019 also allows you to block external access to the Exchange admin center and the Exchange management shell. Instead of relying on network/firewall rules to block access to these features from outside, you can now use client access rules to do so.


Microsoft Exchange Server 2019 offers several performance improvements over previous versions of Exchange Server. For example, Exchange Server 2019 boasts an all-new search infrastructure. It’s rebuilt from the ground up, mirroring the cloud scalability and reliability of Exchange Online. Along with the new search infrastructure comes the ability to index bigger files and better search performance. In addition to better search performance, these improvements also usher in simpler management.

Exchange Server 2019 offers faster and more reliable DAG failovers as well, due to the changes in search infrastructure. This improvement will be most noticeable for larger deployments and larger databases.

By making improvements to the core database engine (via the MetaCache Database feature) in Exchange Server 2019, Microsoft has improved overall Exchange performance. With these improvements comes the ability to leverage the newest storage hardware, which includes larger disks (up to 16TB JBODs) and even solid-state drives. These types of performance improvements offer faster login times as well as less latency.

Exchange Server can now be maxed out with 48 CPU cores and as much as 256GB of RAM. This represents a 100 percent increase in the number of cores supported (over Exchange Server 2016) and a 33 percent increase in the amount of RAM that’s supported. Larger organizations will certainly appreciate these improvements.

Dynamic Database Cache (DDC) ensures that actively mounted databases get more cache memory allocated to them while allocating less to passive databases. This differs significantly from previous versions of Exchange Server, where the same amount of cache memory was assigned to both active and passive databases. The overall performance of the Exchange Server is improved as a result.

End-user experience

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In addition to several new features that enhance the “under-the-hood” engine, Exchange 2019 also brings to the table several new and improved features that affect clients and management of clients. The Do Not Forward feature, for example, is similar to Information Rights Management for calendar items — but without IRM deployment requirements. What this feature does is prevent attendees of a calendar invite from forwarding the invite to others. Instead, only the meeting organizer can invite additional people.

Exchange 2019 also introduces additional options for when a user is not in the office. Improvements in the Out of Office feature includes options such as the ability to add events to your calendar that show you as away or out of office. It also introduces an option to quickly cancel or decline meetings that are going to happen while you are out of the office.

Another change to the calendar in Exchange 2019 is the remove-calendarevents cmdlet. This cmdlet allows administrators to cancel meetings that were previously scheduled by a user that has since left the company. This new cmdlet solves the long-standing headache of attendees being stuck with defunct meetings on their calendars permanently.

Exchange 2019 also introduces updates to the Add-FolderPermissions cmdlet. With this cmdlet, an administrator can now more easily assign delegate permissions via PowerShell.

By incorporating email address internationalization (EAI), Exchange 2019 can now route and natively delivery emails to addresses that contain non-English characters. This was a long-standing headache for administrators in the past that has been put to rest with the newest edition of Exchange Server.

Discontinued features

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If you are coming from an Exchange 2016 environment, you might be surprised to find that unified messaging has been removed from Exchange 2019. As a result, Microsoft is pushing folks to transition to Skype for Business Cloud Voice Mail, instead.

Those coming from Exchange 2013 will notice some additional features and functionality missing from Exchange 2019. For example, the client access server role no longer exists. Instead, it’s been replaced by Client Access services, which run on the mailbox server role — which essentially now provides all of the functionality that the Client Access server role previously provided.

Another feature change between Exchange 2013 and Exchange 2019 is the replacement of the MAPI/CDO library with Exchange Web Services, Exchange ActiveSync, and REST APIs. Organizations that leverage apps that use the MAPI/CDO library need to move them to Exchange Web Services, Exchange ActiveSync, or the REST APIs if they need to continue communicating with Exchange 2019.

Features that have been de-emphasized

Before deploying Exchange 2019, it’s important to consider not only which features have been added and removed, but also which features are being de-emphasized. This is important because it’s a clear signal that future versions of Exchange, if there are any, are likely to eliminate such de-emphasized features. Features that are being de-emphasized in Exchange 2019 include third-party replication APIs, RPC over HTTP, and DAG support for failover administrative access points.

An important caveat….

If you have Exchange Server 2019 installed on Windows 2019 Server Core, pay attention. A rather glaring known issue affects deployments when you try to uninstall Exchange Server from Windows 2019 Server Core via the Exchange Setup Wizard. Not to put too fine a point on it – the operation will fail. I’m not sure how it goes through QA but the uninstall wizard tries to launch the Windows Control Panel to uninstall Exchange. The problem? The Control Panel doesn’t exist in Windows Server Core. As such, if you need to uninstall Exchange from Windows Server Core, use the command below instead:

Setup.exe /IAcceptExchangeServerLicenseTerms /mode:Uninstall

Microsoft indicates that this issue will be addressed in a future CU update for Exchange Server 2019. Which means, whenever that is.

Exchange Server 2019: End of the line?

As an engineer myself, I can certainly appreciate the improvements that Exchange 2019 has made to security and performance — because many of the Exchange servers I’ve supported have been rather large. Most interesting to me is the improved search infrastructure. For me, this is a huge improvement — largely because a few Exchange 2013 servers that I support host thousands of mailboxes across multiple data stores, across multiple DAGs.

The search index on Exchange 2013, especially on larger servers, can be a chore to deal with. There’s nothing like trying to perform a controlled DAG failover, only to find that the content indexes are all out of whack. Bringing them back to a healthy state before performing a failover always made my day! Along with the improved search infrastructure, comes improved failover — in both speed and reliability. I’m cool with that!

Putting my security hat on, I really like the idea of running Exchange on server core. For whatever reason, this was never an option on prior versions. I never understood why it was so crucial that the GUI be available. Although I am largely a late adopter of Windows Server Core, I eventually came around. The ability to install Exchange 2019 and host it on core gives me that much more peace at night when I think about attack surfaces and all of that other fun security-related stuff.

My personal opinion is that Exchange Server 2019 is likely to be the end of the line for Exchange, in its present form as an on-prem solution. That being said, Exchange 2019 is likely to be around for several years, much like its predecessors. What’s clear is that Microsoft appears, at least for the time begin, to not have abandoned its flagship messaging product. If you are currently running Exchange 2013 or Exchange 2016 and aren’t quite ready to move to the cloud yet, Exchange 2019 is something to consider.

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2 thoughts on “Under the hood: What’s new in Exchange Server 2019”

  1. I hope you are wrong about exchange 2019 being the last on prem edition. We are in the hosting business and this would cause a major disruption for us if this is the end of the line for on prem exchange. Microsoft needs to think about its partners too before just abandoning the product.

  2. Nice article Thomas,

    @ Michael – Exchange 2019 is the last on premise edition. This does not mean that it is end of the life for on premise exchange. Microsoft wont abandoning the product, its there next in line bread and butter. This will unfortunately only be available to volume license customers only. Hope that answers your question. We are in the same position where our mail data is not to be stored in the cloud and we moving to Exchange 2019 on premise.

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